1. Field of Invention
The invention relates to an inkjet print head module and the method for making the same. More particularly, it relates to a porous back-shooting inkjet print head module with a tightly sealed ink chamber and the method of manufacturing the same.
2. Related Art
The computer-related products have been widely used to all sorts of applications in various fields. In particular, the convenience of inkjet printers is most welcomed by the public. The print head of a conventional inkjet printer is a thermal inkjet print head. The working principle of this type of print heads is to supply a pulse voltage to a control chip. The voltage signal goes through a heater with high resistance and generates heat. The ink is heated into thermal bubbles. The ink droplets produced by such thermal bubbles are then ejected out of a nozzle onto paper or the surface of other objects. An ink channel is further provided to supply ink from an ink cartridge to an ink chamber.
FIG. 1 shows the structure of a conventional thermal bubble inkjet print head. A thermal barrier 202 is formed on a substrate 201. A resistor heating layer is formed on the thermal barrier 202. The thermal barrier 202 is used to prevent heat generated by the resistor heating layer 203 from entering the substrate 201. The resistor heating layer 203 is covered with a conductor layer 204 with low resistance, which is used to transmit voltage signals. An insulator layer 205 is formed on the conductor layer 204. An adhesion layer 206 is formed along the border of the insulator layer 205 and connects with a nozzle plate 209. The enclosed space is an ink chamber 207. One end of the ink chamber 207 has an ink channel for supplying ink from the ink cartridge to the ink chamber 207. When a pulse voltage signal is sent through the conductor layer 204 to the resistor heating layer 203, heat is generated to produce a thermal bubble 211 from the ink inside the ink chamber 207. The instantaneous pressure increase pushes the ink inside the ink chamber 207 toward and out of the nozzle 210, forming an ink droplet 212.
However, at the same time when the thermal bubble 211 is generated and ejects an ink droplet 212 out of the nozzle 210, the existence of the ink channel 208 often results in loss of the ejection pressure. Moreover, this type of inkjet print heads requires a precision sand blasting process to manufacture a hollow ink reservoir connecting the ink cartridge and the ink channel 208. The nozzle plate 209 and other relevant elements require precision alignment techniques to perform positioning and adhesion. This does not only time-consuming but also results in a low yield. The production cost, on the other hand, is higher. There are more and more high-viscosity inks on the market. The conventional print head structure is not suitable for such applications because of its sealing problem.
In the U.S. Pat. No. 5,940,099, Karlinski et. al. proposed an inkjet print head with ink supply through a porous medium. It mainly includes a piezoelectric material, a deflection layer, an ink supply layer, and a glass capillary. The working principle is to impose a voltage on the piezoelectric material to generate a deformation, ejecting the stored ink. However, the elements used in this method all require precision machining, alignment, and assembly technologies. Therefore, it has a higher cost and longer assembling time.